Edwards-Curve Digital Security Algorithm (EdDSA) for DNSSEC
How DNSSEC zones can sign their records with the Ed25519 and Ed448 EdDSA algorithms.
Sury, O. and R. Edmonds, "Edwards-Curve Digital Security Algorithm (EdDSA) for DNSSEC", RFC 8080, DOI 10.17487/RFC8080, February 2017, <https://www.rfc-editor.org/info/rfc8080>.
@misc{rfc8080,
series = {Request for Comments},
number = 8080,
howpublished = {RFC 8080},
publisher = {RFC Editor},
doi = {10.17487/RFC8080},
url = {https://www.rfc-editor.org/info/rfc8080},
author = {O. Sury and R. Edmonds},
title = {{Edwards-Curve Digital Security Algorithm (EdDSA) for DNSSEC}},
pagetotal = 7,
year = 2017,
month = feb,
} RFC text
Contents
Internet Engineering Task Force (IETF) O. Sury
Request for Comments: 8080 CZ.NIC
Category: Standards Track R. Edmonds
ISSN: 2070-1721 Fastly
February 2017
Edwards-Curve Digital Security Algorithm (EdDSA) for DNSSEC
Abstract
This document describes how to specify Edwards-curve Digital Security
Algorithm (EdDSA) keys and signatures in DNS Security (DNSSEC). It
uses EdDSA with the choice of two curves: Ed25519 and Ed448.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8080.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. DNSKEY Resource Records . . . . . . . . . . . . . . . . . . . 2
4. RRSIG Resource Records . . . . . . . . . . . . . . . . . . . 3
5. Algorithm Number for DS, DNSKEY, and RRSIG Resource Records . 3
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 3
6.1. Ed25519 Examples . . . . . . . . . . . . . . . . . . . . 3
6.2. Ed448 Examples . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
DNSSEC, which is broadly defined in [RFC4033], [RFC4034], and
[RFC4035], uses cryptographic keys and digital signatures to provide
authentication of DNS data. Currently, the most popular signature
algorithm in use is RSA. GOST [RFC5933] and NIST-specified elliptic
curve cryptography [RFC6605] are also standardized.
[RFC8032] describes the elliptic curve signature system Edwards-curve
Digital Signature Algorithm (EdDSA) and recommends two curves,
Ed25519 and Ed448.
This document defines the use of DNSSEC's DS, DNSKEY, and RRSIG
resource records (RRs) with a new signing algorithm, EdDSA, using a
choice of two curves: Ed25519 and Ed448.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. DNSKEY Resource Records
An Ed25519 public key consists of a 32-octet value, which is encoded
into the Public Key field of a DNSKEY resource record as a simple bit
string. The generation of a public key is defined in Section 5.1.5
of [RFC8032].
An Ed448 public key consists of a 57-octet value, which is encoded
into the Public Key field of a DNSKEY resource record as a simple bit
string. The generation of a public key is defined in Section 5.2.5
of [RFC8032].
4. RRSIG Resource Records
An Ed25519 signature consists of a 64-octet value, which is encoded
into the Signature field of an RRSIG resource record as a simple bit
string. The Ed25519 signature algorithm and verification of the
Ed25519 signature are described in Sections 5.1.6 and 5.1.7 of
[RFC8032], respectively.
An Ed448 signature consists of a 114-octet value, which is encoded
into the Signature field of an RRSIG resource record as a simple bit
string. The Ed448 signature algorithm and verification of the Ed448
signature are described in Sections 5.2.6 and 5.2.7 of [RFC8032],
respectively.
5. Algorithm Number for DS, DNSKEY, and RRSIG Resource Records
The algorithm number associated with the use of Ed25519 in DS,
DNSKEY, and RRSIG resource records is 15. The algorithm number
associated with the use of Ed448 in DS, DNSKEY, and RRSIG resource
records is 16. This registration is fully defined in the IANA
Considerations section.
6. Examples
6.1. Ed25519 Examples
Private-key-format: v1.2
Algorithm: 15 (ED25519)
PrivateKey: ODIyNjAzODQ2MjgwODAxMjI2NDUxOTAyMDQxNDIyNjI=
example.com. 3600 IN DNSKEY 257 3 15 (
l02Woi0iS8Aa25FQkUd9RMzZHJpBoRQwAQEX1SxZJA4= )
example.com. 3600 IN DS 3613 15 2 (
3aa5ab37efce57f737fc1627013fee07bdf241bd10f3b1964ab55c78e79
a304b )
example.com. 3600 IN MX 10 mail.example.com.
example.com. 3600 IN RRSIG MX 3 3600 (
1440021600 1438207200 3613 example.com. (
Edk+IB9KNNWg0HAjm7FazXyrd5m3Rk8zNZbvNpAcM+eysqcUOMIjWoevFkj
H5GaMWeG96GUVZu6ECKOQmemHDg== )
Private-key-format: v1.2
Algorithm: 15 (ED25519)
PrivateKey: DSSF3o0s0f+ElWzj9E/Osxw8hLpk55chkmx0LYN5WiY=
example.com. 3600 IN DNSKEY 257 3 15 (
zPnZ/QwEe7S8C5SPz2OfS5RR40ATk2/rYnE9xHIEijs= )
example.com. 3600 IN DS 35217 15 2 (
401781b934e392de492ec77ae2e15d70f6575a1c0bc59c5275c04ebe80c
6614c )
example.com. 3600 IN MX 10 mail.example.com.
example.com. 3600 IN RRSIG MX 3 3600 (
1440021600 1438207200 35217 example.com. (
5LL2obmzdqjWI+Xto5eP5adXt/T5tMhasWvwcyW4L3SzfcRawOle9bodhC+
oip9ayUGjY9T/rL4rN3bOuESGDA== )
6.2. Ed448 Examples
Private-key-format: v1.2
Algorithm: 16 (ED448)
PrivateKey: xZ+5Cgm463xugtkY5B0Jx6erFTXp13rYegst0qRtNsOYnaVpMx0Z/c5EiA9x
8wWbDDct/U3FhYWA
example.com. 3600 IN DNSKEY 257 3 16 (
3kgROaDjrh0H2iuixWBrc8g2EpBBLCdGzHmn+G2MpTPhpj/OiBVHHSfPodx
1FYYUcJKm1MDpJtIA )
example.com. 3600 IN DS 9713 16 2 (
6ccf18d5bc5d7fc2fceb1d59d17321402f2aa8d368048db93dd811f5cb2
b19c7 )
example.com. 3600 IN MX 10 mail.example.com.
example.com. 3600 IN RRSIG MX 3 3600 (
1440021600 1438207200 9713 example.com. (
Nmc0rgGKpr3GKYXcB1JmqqS4NYwhmechvJTqVzt3jR+Qy/lSLFoIk1L+9e3
9GPL+5tVzDPN3f9kAwiu8KCuPPjtl227ayaCZtRKZuJax7n9NuYlZJIusX0
SOIOKBGzG+yWYtz1/jjbzl5GGkWvREUCUA )
Private-key-format: v1.2
Algorithm: 16 (ED448)
PrivateKey: WEykD3ht3MHkU8iH4uVOLz8JLwtRBSqiBoM6fF72+Mrp/u5gjxuB1DV6NnPO
2BlZdz4hdSTkOdOA
example.com. 3600 IN DNSKEY 257 3 16 (
kkreGWoccSDmUBGAe7+zsbG6ZAFQp+syPmYUurBRQc3tDjeMCJcVMRDmgcN
Lp5HlHAMy12VoISsA )
example.com. 3600 IN DS 38353 16 2 (
645ff078b3568f5852b70cb60e8e696cc77b75bfaaffc118cf79cbda1ba
28af4 )
example.com. 3600 IN MX 10 mail.example.com.
example.com. 3600 IN RRSIG MX 3 3600 (
1440021600 1438207200 38353 example.com. (
+JjANio/LIzp7osmMYE5XD3H/YES8kXs5Vb9H8MjPS8OAGZMD37+LsCIcjg
5ivt0d4Om/UaqETEAsJjaYe56CEQP5lhRWuD2ivBqE0zfwJTyp4WqvpULbp
vaukswvv/WNEFxzEYQEIm9+xDlXj4pMAMA )
7. IANA Considerations
This document updates the IANA registry "Domain Name System Security
(DNSSEC) Algorithm Numbers". The following entries have been added
to the registry:
+--------------+----------+----------+
| Number | 15 | 16 |
| Description | Ed25519 | Ed448 |
| Mnemonic | ED25519 | ED448 |
| Zone Signing | Y | Y |
| Trans. Sec. | * | * |
| Reference | RFC 8080 | RFC 8080 |
+--------------+----------+----------+
* There has been no determination of standardization of the use of
this algorithm with Transaction Security.
8. Security Considerations
The security considerations of [RFC8032] and [RFC7748] are inherited
in the usage of Ed25519 and Ed448 in DNSSEC.
Ed25519 is intended to operate at around the 128-bit security level
and Ed448 at around the 224-bit security level. A sufficiently large
quantum computer would be able to break both. Reasonable projections
of the abilities of classical computers conclude that Ed25519 is
perfectly safe. Ed448 is provided for those applications with
relaxed performance requirements and where there is a desire to hedge
against analytical attacks on elliptic curves.
These assessments could, of course, change in the future if new
attacks that work better than the ones known today are found.
A private key used for a DNSSEC zone MUST NOT be used for any other
purpose than for that zone. Otherwise, cross-protocol or cross-
application attacks are possible.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<http://www.rfc-editor.org/info/rfc4033>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005,
<http://www.rfc-editor.org/info/rfc4034>.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
<http://www.rfc-editor.org/info/rfc4035>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <http://www.rfc-editor.org/info/rfc7748>.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017,
<http://www.rfc-editor.org/info/rfc8032>.
9.2. Informative References
[RFC5933] Dolmatov, V., Ed., Chuprina, A., and I. Ustinov, "Use of
GOST Signature Algorithms in DNSKEY and RRSIG Resource
Records for DNSSEC", RFC 5933, DOI 10.17487/RFC5933, July
2010, <http://www.rfc-editor.org/info/rfc5933>.
[RFC6605] Hoffman, P. and W. Wijngaards, "Elliptic Curve Digital
Signature Algorithm (DSA) for DNSSEC", RFC 6605,
DOI 10.17487/RFC6605, April 2012,
<http://www.rfc-editor.org/info/rfc6605>.
Acknowledgements
Some of the material in this document is copied liberally from
[RFC6605].
The authors of this document wish to thank Jan Vcelak, Pieter Lexis,
Kees Monshouwer, Simon Josefsson, Paul Hoffman, and others for a
review of this document.
Authors' Addresses
Ondrej Sury
CZ.NIC
Milesovska 1136/5
Praha 130 00
Czech Republic
Email: ondrej.sury@nic.cz
Robert Edmonds
Fastly
Atlanta, Georgia
United States of America
Email: edmonds@mycre.ws
AI ELI5
On this page
§1Adding EdDSA to DNSSEC
DNSSEC uses cryptographic keys and digital signatures to authenticate DNS data. It is broadly defined in RFC 4033, RFC 4034 and RFC 4035. When this RFC was written, RSA was the most popular signature algorithm in use, with GOST (RFC 5933) and NIST elliptic curve cryptography (RFC 6605) also standardized.
RFC 8032 describes the Edwards-curve Digital Signature Algorithm (EdDSA) and recommends two curves, Ed25519 and Ed448. RFC 8080 defines how DNSSEC's DS, DNSKEY and RRSIG records work with EdDSA using either curve.
DNS already had a few kinds of stamps to prove a record is genuine. This adds a new kind, in two sizes.
§2Public Keys in DNSKEY Records
An Ed25519 public key is a 32-octet value. An Ed448 public key is a 57-octet value. In both cases it is placed in the Public Key field of a DNSKEY record as a simple bit string.
The RFC does not invent a new key format. Key generation is defined in RFC 8032: Section 5.1.5 for Ed25519 and Section 5.2.5 for Ed448.
The public key is like the pattern of a lock that anyone may look at. It is stored as plain bytes, short for one curve and a bit longer for the other.
§3Signatures in RRSIG Records
An Ed25519 signature is a 64-octet value and an Ed448 signature is a 114-octet value. Each goes into the Signature field of an RRSIG record as a simple bit string.
The signing and verification procedures come straight from RFC 8032: Sections 5.1.6 and 5.1.7 for Ed25519, and Sections 5.2.6 and 5.2.7 for Ed448.
The signature is the stamp itself, stored as a fixed run of bytes. A bigger stamp means a bigger safety margin.
§4Algorithm Numbers and IANA
The algorithm number is 15 for Ed25519 and 16 for Ed448. The same number is used in DS, DNSKEY and RRSIG records.
The RFC adds both to the IANA registry Domain Name System Security (DNSSEC) Algorithm Numbers. The mnemonics are ED25519 and ED448, and both are marked as usable for zone signing. For transaction security, no determination of standardization has been made.
Each kind of stamp gets a number so a record can say which one it uses: 15 for the smaller, 16 for the bigger.
| Item | Ed25519 | Ed448 |
|---|---|---|
| Algorithm number | 15 | 16 |
| Public key | 32 octets | 57 octets |
| Signature | 64 octets | 114 octets |
| Security level | around 128-bit | around 224-bit |
§5Test Examples
The RFC gives two sample key sets for each curve. Each shows a private key, a DNSKEY record with flags 257, protocol 3 and the algorithm number, a matching DS record with digest type 2, an MX record and the RRSIG over that MX record, all for example.com. with a TTL of 3600.
Implementers can use them to check that their signing and verification produce matching output.
The document includes worked answers, like the back of a math book, so builders can check their own results.
§6Security Considerations
The security considerations of RFC 8032 and RFC 7748 are inherited. Ed25519 is intended to operate at around the 128-bit security level and Ed448 at around the 224-bit level. A sufficiently large quantum computer would be able to break both. The RFC calls Ed25519 perfectly safe against reasonable projections of classical computers, and offers Ed448 for applications with relaxed performance requirements that want to hedge against analytical attacks on elliptic curves. It notes these assessments could change if better attacks are found.
A private key used for a DNSSEC zone MUST NOT be used for any other purpose than that zone, otherwise cross-protocol or cross-application attacks are possible.
Both stamps are very hard to fake today, and the bigger one has extra margin. Never use your zone's secret stamp for anything else.